Coil form



United States Patent COIL FORM Clayton A. Washburn, Chicago, 111., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application February 21, 1946, Serial No. 649,428

2 Claims. (Cl. 242-419) This invention relates to electromagnetic apparatus, and more particularly to a coil form for minimizing distributed capacitance by permitting the assembly of prefabricated sectional windings into coils.

It is well known to those skilled in the art that there is associated with multi-turn coils a physical phenomenon known as distributed capacitance. While this distributed capacitance results in no particularly ill effects in connection with coils designed for direct current machinery, or coils designed for use at ordinary power frequencies, the effects of this phenomenon become increasingly troublesome as the frequency employed increases. This is particularly true in connection with such applications as cathode ray deflection yoke coils and high voltage pulse transformer coils.

It is an object of this invention to provide a novel form for the assembly of pre-fabricated sectional windings into coils.

A further object of this invention is to provide a coil form readily permitting assembly of pre-fabricated sectional windings into coils of low distributed capacitance.

A still further object of this invention is to provide a coil form for use in connection with cores of rectangular cross section.

Still another object of this invention is to provide a coil form constructed entirely of insulating materials.

Still another object of this invention is to provide a coil form which, when assembled with sectional windings, will produce a rigid self supporting structure which is independent of external fastening means for insuring the retention of its parts in a fixed relationship to each other.

These and other objects will be apparent from the following specification when taken with the accompanying drawings, in which:

Fig. 1 is a plan view of an assembled coil form constructed according to the invention.

Fig. 2 is an end sectional view of Fig. 1 taken along the line II--Il of Fig. 1.

Fig. 3 is a plan view of one of two similar side plate elements.

Fig. 4 is a plan view of one of a plurality of similar coil separator elements.

Fig. 5 is a plan view of one of two similar spacer elements.

Fig. 6 is an end sectional view of Fig. 5 along the line VIVI of Fig. 5.

Referring to the drawings, Fig. 1 and Fig. 2 illustrate an assembled coil form in one embodiment of the present invention. As shown, a plurality of similar separators 11, 12, 13, 14, and 15 are held in place by means of a pair of similar spacers 16 and 17, which in turn are held by a pair of similar slidable side plates 18 and 19, forming a self supporting integral unit. Details of the side plates 18 and 19 are shown in Fig. 3; of the separators 11, 12, 13, 14, 15, in Fig. 4; and of the spacers 16 and 17 in Fig. 5 and Fig. 6. As shown in Fig. 3, side plate 18 which is an illustration of one of two similar members used in the assembly of the coil form consists of a flat plate which extends substantially the width and length of the form. A plurality of separators similar to that shown in Fig. 4 may be mounted in slots such as slots 20, 21, 22, 23, 24 provided in spacers such as spacer 16 illustrated in Fig. 5. As shown in Fig. 6, the spacers consist of a curved section 25 and a reduced boss 27. It will be apparent from the following description that the curved portion 25 provides a smooth surface over which coils may be wound. Likewise, boss 27 provides a pair of flat surfaces upon which the side plates may be slidably mounted.

Assembly of the elements with pre-fabricated windings to produce a coil assembly with low distributed capacitance is accomplished by stacking the required number of windings alternately with separators 11, 12, 13, 14 and 15. The spacers 16 and 17 are next inserted so that the slots 20, 21, 22, 23 and 24 are engaged by the separators 11, 12, 13, 14 and 15. It is now possible to slide in the plates 18 and 19 making a complete self supporting assembly, which may be impregnated with a dielectric liquid and baked if desired for better moisture proofing and insulating qualities. It may be used as an air core inductor, or it may be placed over a rectangular ferro-magnetic core. The radii 25 and 26 are incorporated on the spacers 16 and 17 to eliminate sharp bends in the wire used in the windings at the corners of the form.

The coil form as contemplated by this invention may be made entirely of insulating material thereby eliminating all metal from the form. Among the many insulating materials which may be employed are linen base bakelite and molded ceramics, for example. While a coil form for mounting sectional coils on rectangular cores has been described, it will readily be understood that the shape of the form may be varied as may be found to be desirable. Likewise, while in the embodiment described a hollow core is illustrated, a ferro magnetic core may be employed if this is desirable.

While a particular embodiment of this invention has been disclosed and described, it is to be understood that various changes and modifications may be made therein without departing from the spirit and scope of the appended claims.

What is claimed is:

l. A rectangular coil form for mounting prefabricated windings, comprising a pair of spacers, each spacer having two longitudinal recesses adjacent inner edges respectively thereof and a plurality of transverse slots cut through an outer surface thereof, two end and at least one intermediate separators having openings encircling both spacers and mounted in said slots therein, and a pair of side plates positioned within said separator openings, and each of said side plates extending between said pair of spacers and being seated in one recess of each of said spacers, constituting therewith, when the side plates are in position, a self-supporting coil from whereof the diagonal greatly exceeds the interspacing of the separators.

2. A rectangular coil form of the type defined by claim 1 wherein the surfaces of the spacers between the transverse slots are curved.

References Cited in the file of this patent UNITED STATES PATENTS 1,104,032 Anderson July 21, 1914 1,136,431 Morse Apr. 20, 1915 2,225,593 McArn Dec. 17, 1940 2,229,413 Joost Jan. 21, 1941 2,355,477 Stahl Aug. 8, 1944 FOREIGN PATENTS 486,535 Great Britain June 7, 1938 105,776 Sweden Oct. 27, 1942 

